Executive Summary
An arXiv paper describes a 'Toxic Agent Flow' attack against the GitHub MCP server, using malicious GitHub issues to hijack a user's agent and leak private repository data.
What Happened
This paper describes a 'Toxic Agent Flow' attack against the GitHub MCP server. The attack uses malicious GitHub issues to hijack a user's agent and leak private repository data.
Affected Products
- GitHub MCP server
Vulnerability / Attack Technique
Prompt injection via issues through an MCP server
Technical Mechanism
The agent reads a malicious issue through the MCP server and follows instructions to expose private repo data.
AI Security Category
LLM01:2025 Prompt Injection
Part of the Prompt Injection topic.
Part of the MCP Security topic.
Relevant Frameworks
RealGround Analysis
MCP servers bring public content into private contexts. RealGround analysis: scope MCP tokens so agents reading public issues cannot reach private repos.
Recommended Controls
- Scope GitHub MCP tokens per repository
- Treat issue content as untrusted
Related RealGround Service
Secure AI Agent Build · or start with the free AI Agent Security Scanner.
Sources
arXiv: https://arxiv.org/html/2506.23260v1
Summary and analysis written by RealGround from the source above; last updated 2026-10-18.